Otolith Development, Increment Formation, and an Uncoupling of Otolith to Somatic Growth Rates in Larval and Juvenile Goldfish

Abstract

Growth rate effects on the relationship between otolith size and body size were examined in larval and juvenile goldfish. They were kept under the same environmental and feeding conditions, and sampled ad libitum until 154 days after hatching. Therefore, their variations in body size will be explained by internally mediated constraints on growth. After measurement of body size in standard length, three kinds of otolith were dissected under a binocular microscope and their morphological changes were noted. The asteriscus was too small to be dissected consistently at hatching. The sagitta was considerably deformed with growth. The lapillus was relatively large at hatching and grew steadily from a round to a pear shape. For this reason, lapilli alone were used to measure otolith length (diameter or long axis) and to count the number of otolith increments. Otoliths had three increments at hatching and subsequent increments deposited on a daily basis until at least 154 days after hatching. The relationship between otolith and body length showed an excellent correlation (r=0.92-0.97) within three groups which had different growth rates. However, analysis of covariance revealed a different slope of regression among the groups. This indicates that slow-growing fish have larger otoliths than equal-sized, rapidly growing fish. © 1992, The Japanese Society of Fisheries Science. All rights reserved.